JP2015193000A - Adsorbent and halitosis remover - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adsorbent which effectively adsorbs hydrogen sulfide which causes halitosis, in contrast to a conventional technique where hydrotalcite containing Mg as a divalent metal and Al as a trivalent metal had been proposed, which however had problems that this hydrotalcite needed a heat treatment such that it lost a layer structure after synthesis and that its adsorption capacity for hydrogen sulfide decreased by the presence of moisture.SOLUTION: The adsorbent comprises hydrotalcite having a structure represented by formula (2), and adsorbs a volatile sulfur compound in a liquid phase: [ZnAl(OH)][COmHO] (2), where 0<x<1, and m is an integer larger than zero. The adsorbent adsorbs hydrogen sulfide very well, whether in liquid phase or gas phase, and without performing a heat treatment after synthesis.

Description

  The present invention relates to an adsorbent that adsorbs volatile sulfur compounds, particularly hydrogen sulfide, well.

Hydrotalcite is a layered double hydroxide having an anion exchange function, and the general formula is represented by the formula (1).
^{_{[M m 2+ M n 3+ (}} OH) 2m + 2n] X n / z Z- bH 2 O (1)

Here, M _m ²⁺ is at least one divalent metal selected from Mg, Ca, Sr, Cu, Ba, Zn, Cd, Pb, Ni, and Sn, and M _n ³⁺ is Al, Fe, Cr , Ga, Ni, Co, Fe, Mn, Cr, V, Ti, and In, m and n are real numbers, ^XZ− is a Z-valent anion, and b is a real number.

For example, even when Zn is selected as M _m ²⁺ , hydrotalcite is used as an adsorbent in various aspects. For example, in Patent Document 1, nitrite ions are adsorbed. In Patent Document 2, nitrate ions are adsorbed.

  Moreover, in patent document 3, in order to collect | recover silver, silver is made to adsorb | suck to a hydrotalcite. Moreover, in patent document 4, in order to remove hydrogen fluoride, hydrogen fluoride is made to adsorb | suck to a hydrotalcite.

  Among the substances to be adsorbed, there is a high demand for adsorbing and deodorizing malodorous substances such as hydrogen sulfide and methyl mercaptan mainly composed of sulfur compounds. Patent Document 5 reports that a mixture of hydroxylamine sulfate, an organic hydrazide compound, and a mixture of zinc oxide and smectite containing hydrotalcite has an adsorptivity (deodorant) to hydrogen sulfide.

In addition, as a bad breath remover, there is an invention in which a volatile sulfur compound (VSC: Volatile Sulfur Compounds) in a liquid phase is adsorbed on hydrotalcite (see Patent Document 6). Here, an example in which Mg is selected as M _m ²⁺ is disclosed.

JP 2005-336002 A JP 2002-348120 A Japanese Patent Laid-Open No. 9-175819 International Publication No. 2011/074631 JP 2011-30967 A International Publication No. 2012/150459

  Referring to Patent Documents 1 to 5, volatile sulfur compounds such as hydrogen sulfide are in demand for adsorbents (and can be said to be deodorants as a result), but the present situation is that high adsorbents have not been obtained. is there.

On the other hand, Patent Document 6 introduces a hydrotalcite that adsorbs volatile sulfur compounds in water well. However, this is hydrotalcite [Mg ²⁺ _1-x + Al ^{3 +} _x (OH) ₂ ] [CO ₃ ² _{−X / 2} ] which is further heated after the synthesis of hydrotalcite. Therefore, this material has a problem of gradually losing its effect in an atmosphere or moisture containing moisture. There is also a problem that heat treatment at a high temperature of 500 ° C. is necessary to eliminate the layer structure.

  The present invention has been conceived in view of the above problems, and an adsorbent that does not require heat treatment at a high temperature after synthesis and can maintain the adsorption ability of a volatile sulfur compound even when kept in water. It is to provide.

More specifically, the adsorbent according to the present invention is characterized by containing hydrotalcite having the structure of the formula (2).
[Zn ²⁺ _1-x + Al ³⁺ _x (OH) ₂ ] [CO ₃ ²⁻ _{X / 2} · mH ₂ O] (2)
Here, 1 <x <1, and m is an integer greater than zero.

Moreover, the hydrotalcite which has a structure of (3) Formula and (4) Formula is contained, It is characterized by the above-mentioned.
[Mg ²⁺ _1-x + Fe ³⁺ _x (OH) ₂ ] [CO ₃ ²⁻ _{X / 2} · mH ₂ O] (3)
_{^{[Mg 2+ 1-x + Fe}} 3+ x (OH) 2] [Cl - X · mH 2 O] (4)
Hereinafter, the hydrotalcites of the formulas (2), (3), and (4) are referred to as “Zn hydrotalcite”, “carbonated Fe hydrotalcite”, and “chlorine type Fe hydrotalcite”.

  The hydrotalcite according to the present invention does not need to be subjected to heat treatment in order to exhibit the adsorption ability of volatile sulfur compounds. Moreover, even if it hold | maintains in water, the adsorption capacity of a volatile sulfur compound does not fall. For example, even if it is kept in a liquid phase or a high-humidity gas phase environment as in the oral cavity, the volatile sulfur compound is adsorbed over a long period of time, so that it is effective in preventing bad breath.

  Moreover, if it is a gaseous phase or a liquid phase, it will not be limited to an intraoral area, but adsorption | suction (as a result of deodorizing) of a volatile sulfur compound in places, such as a toilet and a trash can, is possible.

It is a figure which shows the structure of the test | inspection apparatus which measures the adsorptivity of a product. It is a graph which shows the time change of the hydrogen sulfide density | concentration (micromol) in a test | inspection apparatus at the time of putting Mg33 hydrotalcite. It is a graph which shows the time change of the hydrogen sulfide concentration (micromol) in a test | inspection apparatus at the time of putting Mg33 hydrotalcite 500. FIG. It is a figure which shows the result of having investigated the X-ray diffraction of Mg33 hydrotalcite 500. FIG. It is a figure which shows the comparison of the adsorption capacity of Mg hydrotalcite 500 and Zn hydrotalcite 500. It is a figure which shows the comparison of the adsorption capacity of Zn hydrotalcite and Zn hydrotalcite 500. It is a figure which shows the X-ray-diffraction pattern of Zn hydrotalcite, Zn hydrotalcite 500, and Zn hydrotalcite 500 after an adsorption test. It is a figure which shows a time-dependent change of the total amount of hydrogen sulfide in the liquid phase in a test | inspection apparatus, and a gaseous phase. It is a figure which shows the result of the X-ray diffraction of the carbonate type Fe hydrotalcite and chlorine type Fe hydrotalcite just after producing | generating and drying. FIG. 10 is an enlarged view of 2θ of FIG. 9 of 10 to 40 °. It is a figure which shows the result of the X-ray diffraction of carbonic acid type Fe hydrotalcite and chlorine type Fe hydrotalcite after being immersed in the hydrogen sulfide aqueous solution with a test | inspection apparatus. It is a figure which shows the result of the X-ray diffraction before immersion of chlorine type Fe hydrotalcite, and after immersion. (A) is a figure which shows the infrared absorption spectrum of carbonate type Fe hydrotalcite, (b) is a figure which shows the infrared absorption spectrum of chlorine type Fe hydrotalcite. (A) is a figure which shows the EDS profile of a carbonate type Fe hydrotalcite, (b) is a chlorine type Fe hydrotalcite.

  Below, the manufacturing method of Zn hydrotalcite concerning the present invention is explained, referring to drawings. The following description shows one embodiment of the present invention, and the following description can be modified without departing from the gist of the present invention.

  Zn hydrotalcite can be produced in the same manner as other hydrotalcites. That is, divalent zinc is prepared as an aqueous salt solution. Trivalent aluminum is also prepared as an aqueous salt solution. These are the raw materials for the host layer. Then, Zn hydrotalcite can be obtained by coprecipitation by adding an alkaline solution to these salt aqueous solutions. The element of the guest layer is determined by the alkaline solution added at this time.

  As the zinc salt aqueous solution, zinc nitrate, zinc sulfate, zinc phosphate, zinc carbonate and the like can be suitably used. Also, aluminum nitrate, aluminum sulfate, aluminum phosphate and the like can be suitably used as the aqueous salt solution of aluminum. In particular, zinc nitrate can be preferably used.

  In addition, an alkaline solution containing carbonic acid can be suitably used. Examples of the carbonate aqueous solution that can be used include sodium carbonate, potassium carbonate, calcium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, ammonium carbonate, and mixtures thereof (may be dolomite). In particular, sodium carbonate can be suitably used.

  These solutions are mixed and reacted. For the reaction, a method such as stirring or heating may be used. The product produced by the reaction is subjected to a heat treatment. The heat is 100 ° C. to 400 ° C. and the temperature is about 4 to 10 hours to obtain Zn hydrotalcite.

  Moreover, the Zn hydrotalcite used for the adsorbent according to the present invention may not be subjected to heat treatment. Usually, hydrotalcite becomes an anhydrate by heat treatment after the reaction is generated, and exhibits an adsorption ability. However, this is because the Zn hydrotalcite used in the adsorbent according to the present invention has the ability to absorb volatile sulfur compounds without being subjected to heat treatment.

  Carbonic acid type Fe hydrotalcite and chlorine type Fe hydrotalcite according to the present invention can also be obtained in the same manner. That is, divalent magnesium is prepared as an aqueous salt solution. Trivalent iron is also prepared as an aqueous salt solution. These are the raw materials for the host layer. Then, an alkaline solution is added to these salt aqueous solutions to cause coprecipitation. The element of the guest layer is determined by the kind of the alkaline solution added at this time.

  As the magnesium salt aqueous solution, magnesium nitrate, magnesium sulfate, magnesium phosphate, magnesium carbonate and the like can be suitably used. Moreover, iron nitrate, iron sulfate, iron phosphate, etc. can be utilized suitably for the salt solution of iron. In particular, nitrates can be preferably used for both magnesium and iron.

  Moreover, as an alkaline solution, what contains carbonic acid can be utilized. However, it is sufficient that the pH in the reaction solution is alkaline, and the reaction solution may be prepared while adjusting the pH with a strong alkali solution such as sodium hydroxide. In carbonated Fe hydrotalcite, sodium carbonate or the like can be suitably used as the alkaline solution.

  In the case of chlorine type Fe hydrotalcite, a sodium chloride solution is added while adding sodium hydroxide. This is because coprecipitation can be stably obtained on the alkali side.

  Since the hydrotalcite according to the present invention has the ability to adsorb VOC, it may be added to the bad breath remover. The bad breath remover is mainly composed of monoglyceride and the like, and contains an additive such as polyol and a bad breath remover.

  Moreover, the bad breath removing agent according to the present invention may include a dentifrice and an oropharyngeal drug. Dentifrices include abrasives such as calcium hydrogen phosphate, calcium carbonate, and aluminum hydroxide, foaming agents such as lauroyl sarcosoda, sodium lauryl sulfate, and sucrose fatty acid esters, and humectants such as sorbitol, glycerin, and propylene glycol The hydrotalcite of the present invention may be included with a binder such as alginic acid.

  In addition, the oropharyngeal drug contains components such as cetylpyridinium chloride hydrate, dipotassium glycyrrhizinate, and a red pepper extract. The adsorbent of the present invention can be included in an oropharyngeal drug along with these components.

  Next, a method for measuring the characteristics of the product will be described. About the adsorption capacity (adsorbability) of the volatile sulfur compound of the product, the adsorption capacity of hydrogen sulfide in the gas phase in contact with the liquid phase and the liquid phase was measured. FIG. 1 shows an inspection apparatus 1 that measures adsorption capacity. The inspection apparatus 1 has a threaded side tube attached to a commercially available 200 mL glass flask 2 and a septum-attached hole cap 6 attached to the side tube. Moreover, the separatory funnel 3 with a cock was attached to the opening | mouth of the glass flask 2 through the silicone stopper. From the hole cap 6 with a septum, the needle of the syringe 5 can enter the glass flask 2 to extract the internal gas or liquid. Note that a stirring bar is placed in the inspection apparatus 1. This inspection apparatus 1 was used as follows.

  First, the glass flask 2 was filled with 150 mL of an aqueous hydrogen sulfide solution (reference numeral 10). The portion of the hydrogen sulfide aqueous solution 10 is a liquid phase portion, and the head space 11 in contact with it is a gas phase portion. Hydrogen sulfide water was adjusted so that hydrogen sulfide gas was bubbled and the initial concentration became a constant value. An inspection apparatus 1 was prepared for each sample of Examples and Comparative Examples described later. A predetermined amount of each of the samples (adsorbents of Examples and Comparative Examples) was introduced into the hydrogen sulfide aqueous solution of the inspection apparatus 1, and the gas phase and liquid phase after 1 hour, 2 hours, 3 hours, 4 hours, 6 hours and 18 hours The VSC concentration was examined. Depending on the example, the measurement was also performed for 5 hours.

The VSC concentration is obtained by sampling a predetermined amount of a test component (gas or liquid) from the gas phase (head space 11) and the liquid phase (in the aqueous solution) in the glass flask 2 with a syringe 5, and using FPD / GC (Frame Photometric Detection / Hydrogen sulfide (H ₂ S) was quantified by Gas Chromatography.

<Example 1>
And 0.02mol of zinc sulfate hexahydrate _{(Zn (NO 3) 2 ·} 6H 2 O), ultrapure water 0.01mol of aluminum nitrate nonahydrate _{(Al (NO 3) 3 ·} 9H 2 O) It melt | dissolved in 100 mL and it was set as the metal salt aqueous solution.

0.047 mol of sodium carbonate (Na ₂ CO ₃ ) was dissolved in 300 mL of ultrapure water to obtain a carbonate aqueous solution. This carbonate aqueous solution was kept at 70 ° C., and the metal salt aqueous solution was added while stirring. Further, 0.05 mol of NaOH dissolved in 100 mL of pure water was added until the pH reached 10. Thereafter, the mixture was aged and stirred for 24 hours. The obtained product was centrifuged and washed until the pH of the washing solution reached about 7.5. Thereafter, it was dried at a temperature of 80 ° C. for 12 hours to obtain Zn hydrotalcite. The obtained product is X = 0.33 in the formula (2).

  In addition, a sample in which the Zn hydrotalcite was further heat-treated at 500 ° C. for 2 hours was produced. This is called Zn hydrotalcite 500.

<Comparative Example 1>
The same materials and procedures as in Example 1 were repeated except that the zinc sulfate hexahydrate of Example 1 was changed to magnesium nitrate hexahydrate (Mg (NO ₃ ) ₂ .6H ₂ O) to obtain hydrotalcite. It was. This is called Mg hydrotalcite. The Mg hydrotalcite was temperature-treated at 500 ° C. for 2 hours. This sample is referred to as Mg hydrotalcite 500.

<Comparative Example 2>
It was dissolved sodium carbonate _(Na 2 CO ₃₎ in ultrapure water, and then aluminum nitrate nonahydrate _{(Al (NO 3) 3 ·} 9H 2 O) and magnesium nitrate hexahydrate (Mg _{(NO 3) 2} · An aqueous solution prepared by dissolving 6H ₂ O) was added dropwise while maintaining the pH at 10. Composition formula ^{_{Mg 1-x Al x (OH}} ) 2 A n- x / n · nH x = 0.33 in ₂ O was adjusted to (the same as in Example 1 and Comparative Example 1).

  A precipitate obtained by stirring at 70 ° C. for 24 hours was filtered off, washed with ultrapure water, and treated at 80 ° C. for 12 hours to obtain a sample. This sample is referred to as Mg33 hydrotalcite (also referred to as “Mg33HT”). Further, the Mg33 hydrotalcite was further heat-treated at 500 ° C. for 30 minutes. This sample is referred to as Mg33 hydrotalcite 500 (also referred to as “Mg33HT500”).

In FIG. 2, the time change of the hydrogen sulfide concentration (micromol) in the test | inspection apparatus 1 at the time of putting Mg33 hydrotalcite as a sample is shown. The vertical axis represents hydrogen sulfide concentration (denoted as H ₂ S concentration (μmol)), and the horizontal axis represents time (hr). The hydrogen sulfide concentration in the liquid phase (A) showed an increasing tendency from the initial stage (0 hour) to 2 to 4 hours, and thereafter showed a gradual decreasing tendency.

  On the other hand, in the gas phase (B), the concentration was almost below the detection limit in 1 hour after the sample was charged. That is, Mg33 hydrotalcite could not absorb hydrogen sulfide in the aqueous solution, but absorbed hydrogen sulfide in the gas phase in contact with the aqueous solution in which hydrogen sulfide was dissolved.

In FIG. 3, the time change of the hydrogen sulfide density | concentration (micromol) in a test | inspection apparatus at the time of putting Mg33 hydrotalcite 500 is shown. The vertical axis represents hydrogen sulfide concentration (denoted as H ₂ S concentration (μmol)), and the horizontal axis represents time (hr). The hydrogen sulfide concentration in the liquid phase (A) showed an increasing tendency from the initial stage (0 hour) to 1 hour, and thereafter showed a decreasing tendency.

  Furthermore, after 18 hours, the hydrogen sulfide concentration in the liquid phase (A) decreased to 15%. Further, in the gas phase (B), as in the case of Mg33 hydrotalcite, the concentration was almost below the detection limit in 1 hour after the sample was charged.

  That is, the Mg33 hydrotalcite 500 was able to absorb hydrogen sulfide in the aqueous solution (liquid phase) and also absorb hydrogen sulfide in the gas phase in contact with the aqueous solution in which hydrogen sulfide was dissolved. .

  In FIG. 4, the result of having investigated the X-ray diffraction of Mg33 hydrotalcite 500 is shown. The vertical axis represents intensity (arbitrary unit), and the horizontal axis represents 2θ (degrees). Co Kα was used as the radiation source. FIG. 4 shows three diffraction results. (A) is a diffraction result of Mg33 hydrotalcite (denoted as “MG33HDT” in FIG. 4) immediately after synthesis.

  Next, (b) is a diffraction result of Mg33 hydrotalcite 500 obtained as a result of heat-treating Mg33 hydrotalcite at 500 ° C. for 2 hours. In (a) and (b), the peak pattern clearly changed, and it is considered that the layered structure of hydrotalcite was changed by the heat treatment at 500 ° C.

  On the other hand, (c) is an X-ray diffraction result of the Mg33 hydrotalcite 500 after the absorption experiment shown in FIG. This gave the same diffraction results as the Mg33 hydrotalcite immediately after synthesis shown in (a).

  From the above results, the Mg33 hydrotalcite 500 heat-treated at 500 ° C. changes its layered structure, and after being put into the liquid phase, restructures the layered structure. Therefore, considering that hydrogen sulfide in the liquid phase and gas phase is absorbed as shown in FIG. 2, intercalation of hydrogen sulfide between the layered structures is performed when the layered structure is reconfigured. It is thought that it is taken in. In other words, in Mg33 hydrotalcite, it can be said that the adsorptive capacity deteriorates due to moisture.

  FIG. 5 is a diagram showing a comparison of the adsorption capacities of Mg hydrotalcite 500 (Comparative Example 1) and Zn hydrotalcite 500. The horizontal axis represents time (hr), and the vertical axis represents the change (%) in hydrogen sulfide concentration. Here, the vertical axis represents the concentration change of the liquid phase and gas phase hydrogen sulfide combined. The black circle is the change when the sample is not inserted, the black rhombus is the change when the sample is Mg33 hydrotalcite 500 (described as “Mg33HDT500” in the figure), and the black triangle is the Zn hydrotalcite. A change in the case of the site 500 (described as “ZnHDT500” in the drawing) is shown.

  It is considered that the Mg hydrotalcite 500 (Comparative Example 1) does not absorb hydrogen sulfide in the liquid phase as quickly as the gas phase, like the Mg33 hydrotalcite 500 (Comparative Example 2) in FIG. On the other hand, it can be seen that Zn hydrotalcite 500 (Example) can rapidly adsorb liquid and gas phase hydrogen sulfide as compared with Mg hydrotalcite 500.

  FIG. 6 shows a comparison of the adsorption capacities of Zn hydrotalcite and Zn hydrotalcite 500. The horizontal axis represents time (hr), and the vertical axis represents the change (%) in hydrogen sulfide concentration. The white square represents the time change of the hydrogen sulfide concentration when there is no sample. Zn hydrotalcite (described as “ZnHDT” in the figure) is a white rhombus, and Zn hydrotalcite 500 (described as “ZnHDT500” in the figure) is represented by a black triangle. As is clear from FIG. 6, the adsorption capacity of Zn hydrotalcite and Zn hydrotalcite 500 was hardly changed.

  In FIG. 7, Zn hydrotalcite (denoted as “ZnHDT”), Zn hydrotalcite 500 (denoted as “ZnHDT500”), and Zn hydrotalcite 500 after the adsorption test (“ZnHDT500 after adsorption”) X-ray diffraction pattern of

  The horizontal axis is 2θ (degrees), and the vertical axis is intensity (arbitrary unit). The heat treatment at 500 ° C. changed the X-ray diffraction profile. Accordingly, it can be said that the layer structure of the Zn hydrotalcite 500 is changed from that of the Zn hydrotalcite. However, after the adsorption test, the layered structure was reconstructed again.

This is the same as the case of Mg33 hydrotalcite shown in FIG. However, the difference from the case of Mg33 hydrotalcite is that the adsorption capacity of hydrogen sulfide hardly changes even if the layered structure of Zn hydrotalcite changes (from the result of FIG. 6). That is, in Zn hydrotalcite, it can be said that the change in the layered structure and the reconstruction are not so much related to the adsorption of hydrogen sulfide (H ₂ S).

  In other words, the adsorption capacity of Zn hydrotalcite is not changed by moisture. Therefore, the adsorption performance of the adsorbent containing Zn hydrotalcite does not change even if it is left in an environment containing moisture, and can quickly absorb and deodorize hydrogen odor source. Also, this adsorbent is very easy to use because it can be deodorized by sprinkling powdered Zn hydrotalcite on a malodorous part, regardless of liquid phase or gas phase.

  Moreover, Zn hydrotalcite may be previously contained in the liquid phase, and the whole liquid phase may be added to a portion having a bad odor. That is, the volatile sulfur compound in the oral cavity can be removed by containing it in the bad breath remover, dentifrice, oropharyngeal drug.

  In the above experiment, the initial concentration of the aqueous hydrogen sulfide solution is 30 ppm, and the sample introduced into the inspection apparatus 1 is 0.2 g. Also, the concentration was measured by sampling 0.2 g each for the liquid phase and the gas phase.

<Example 1-1>
Next, more specific effects of Zn hydrotalcite were confirmed using periodontal disease-related bacteria. The test bacteria used were F. nucleatum (ATCC 25586). This species has been confirmed to produce hydrogen sulfide.

  The test bacteria were cultured as follows. Using Brain Heart Infusion medium (BHI medium, BD, Tokyo) containing 0.5% yeast extract, 5 μg / mL hemin, and 0.5 μg / mL menadione, 2 mL of cultured bacterial solution was anaerobically cultured for 48 hours with sulfur-containing amino acids. A certain amount of 0.05% L-cysteine was added, and the test bacteria were inoculated into 40 mL of a medium that had been anaerobic for 1 day.

  2 mL each of the bacterial solution cultured in the assist tube (Assist, Tokyo) was dispensed, and anaerobic culture was performed at 37 ° C. Mg33 hydrotalcite (Mg33HDT) without heat treatment, Mg33 hydrotalcite (Mg33HDT500) heat-treated at 500 ° C., and 0.01 g of Zn hydrotalcite (ZnHDT) and “no adsorbent” Four types were produced.

  The Mg hydrotalcite 500 was previously heat-treated at 500 ° C. for 30 minutes in an electric furnace. In addition, in order to prevent bacterial product from escaping to the outside air, silicon rubber was put on the assist tube. When measuring hydrogen sulfide, 3 mL of gas in the assist tube was collected with a gas tight syringe and immediately injected into a gas chromatograph, and the peak area of hydrogen sulfide was calculated. Measurement time was performed every 2 hours for 8 hours, and was performed twice in total. Table 1 shows the measurement results after 8 hours.

  In actual bacteria, the amount of hydrogen sulfide produced varies depending on the lot of the strain. Therefore, the amount of hydrogen sulfide is different between the first time and the second time (see “No adsorbent”). However, Zn hydrotalcite has the result of suppressing the generation of hydrogen sulfide most in any experiment.

<Example 2>
Carbonated Fe hydrotalcite was prepared by the coprecipitation method of the following procedure. To 167 mL of ultrapure water, 8.83 g of sodium carbonate (Wako Pure Chemical Industries, volumetric analysis standard substance) was dissolved to prepare a sodium carbonate solution. Moreover, 8.00 g of sodium hydroxide (Wako Pure Chemical Industries, special grade) is dissolved in 100 mL of ultrapure water, and iron nitrate (III) nonahydrate (Wako Pure Chemical Industries, Ltd.) is dissolved in 83 mL of sodium hydroxide solution and ultrapure water. A mixed solution of nitrate in which 8.42 g of special grade and 16.03 g of magnesium nitrate hexahydrate (Wako Pure Chemical Industries, special grade) were dissolved was prepared. Iron and magnesium are the raw materials for the host layer.

  While stirring the sodium carbonate solution with a hot stirrer (ASONE, REXIM RSH-10) using a 4 cm stirrer at 800 rpm at room temperature, the nitrate mixed solution was added to the sodium carbonate solution at 10 mm ± 0.5 / min using a burette. It was dripped at a speed. Carbonic acid is a raw material for the guest layer.

  Although the initial pH of the sodium carbonate solution was 11.7, it was immediately oxidized by the dropwise addition of the nitrate mixed solution, so the sodium hydroxide solution was adjusted so that the pH of the solution would be 10.5 ± 0.2 with a pH meter. added.

This solution was stirred at 800 rpm for 24 h at 40 ° C., and the resulting solution was subjected to solid-liquid separation by suction filtration and washed three times with 200 mL of ultrapure water. The obtained product was dried at 80 ° C. for 18 hours and then crushed in a mortar to obtain carbonated Fe hydrotalcite (also referred to as carbonated Mg—Fe LDH). Note that the carbonate-type Fe hydrotalcite is A ⁿ⁻ = CO ₃ ²⁻ and x = 0.33 in the composition formula (3).

  The pH was measured using a pH meter (HORIBA, D-51), and ultrapure water was collected from an ultrapure water production apparatus (Direct-Q, manufactured by Millipore) and used for experiments.

<Example 3>
Chlorine-type Fe hydrotalcite was prepared by the coprecipitation method of the following procedure. In order to reduce the carbonate ion which dissolved 1000 mL of ultrapure water, it was boiled. 9.74 g of sodium chloride (Wako Pure Chemical Industries, special grade) was dissolved in 167 mL of the ultrapure water to prepare a sodium chloride solution.

  Further, 12.00 g of sodium hydroxide (Wako Pure Chemical Industries, special grade) is dissolved in 150 mL of ultrapure water, and iron (III) nitrate nonahydrate (Wako Pure Chemical Industries, Ltd.) is dissolved in 83 mL of sodium hydroxide solution and ultrapure water. A mixed solution of nitrate in which 8.42 g of special grade and 16.03 g of magnesium nitrate hexahydrate (Wako Pure Chemical Industries, special grade) were dissolved was prepared. Iron and magnesium are the host layer.

  While stirring the sodium carbonate solution with a hot stirrer at 800 rpm at room temperature using a 4 cm stirrer, the mixed solution of nitrate was dropped into the sodium chloride solution at a rate of 10 ± 0.5 mm / min using a burette.

  Since the initial pH of the sodium chloride solution was 7.9, the mixed solution of nitrate was dropped after the sodium hydroxide solution was added and the pH reached 11.7, and the pH of the solution was adjusted to 10.5 ± 0 with a pH meter. The sodium hydroxide solution was added to reach .2.

This solution was stirred at 800 rpm for 24 h at 40 ° C., and the resulting solution was subjected to solid-liquid separation by suction filtration and washed three times with 200 mL of ultrapure water. The obtained product was dried at 80 ° C. for 18 hours and then crushed in a mortar to obtain chlorine-type Fe hydrotalcite (also referred to as chlorine-type Mg—Fe-based LDH). Incidentally, carbonate type Fe hydrotalcite, (4) In the composition formula of ^formula, A ^n- = Cl ^-, is x = 0.33.

  FIG. 8 shows changes over time in the total amount of hydrogen sulfide in the liquid phase and gas phase in the inspection apparatus 1. The vertical axis represents the change (%) in the total hydrogen sulfide amount, and the horizontal axis represents time (h). 100% on the vertical axis is the total concentration of the solution of the inspection apparatus 1 and the hydrogen sulfide in the head space before the sample is charged.

  Here, an aqueous hydrogen sulfide solution was prepared as follows. A 500 mL four-necked flask was fitted with a separatory funnel, two side tubes each with a silicon stopper and a glass stopper with a glass tube. In addition, 150 mL of ultrapure water was placed in a 200 mL glass flask, and a glass tube and a cylindrical gas injection tube were attached through a silicon stopper. The glass tube of the four-neck flask and the cylindrical gas injection tube of the glass flask were connected to the silicon tube via a two-way cock.

  Furthermore, the glass tube of the glass flask was connected to a gas cleaning bottle filled with 1 mol / L sodium hydroxide aqueous solution through a silicon tube. A calcium chloride tube was attached to the gas cleaning bottle via a silicon tube. Add 3 g of iron sulfide (FeS, Wako Pure Chemical Industries, for hydrogen sulfide generation) to a 500 mL four-necked flask, and then dilute sulfuric acid (Wako Pure Chemical Industries, reagent grade) from a separatory funnel at a concentration of 1 mL / L dilute sulfuric acid. In addition, hydrogen sulfide was generated in the flask. The generated hydrogen sulfide was passed through ultrapure water in a glass flask and bubbled for about 15 minutes.

  Referring to FIG. 8, white squares are cases where no adsorbent (carbonated Fe hydrotalcite or chlorine type Fe hydrotalcite) is contained. The cross mark indicates carbonate type Fe hydrotalcite (indicated as “carbonate type FeHDT” in the figure), and the black diamond mark indicates chlorine type hydrotalcite (indicated as “chlorine type FeHDT”).

  Both carbonate-type Fe hydrotalcite and chlorine-type Fe hydrotalcite were greatly reduced as soon as the sample was added, and decreased by 90% in 1 hour. After that, it continued to decrease with time, and after 5 hours, the hydrogen sulfide concentration in the detector 1 decreased to below the detection limit of the measuring device. Thus, both carbonate-type Fe hydrotalcite and chlorine-type hydrotalcite can adsorb VSC in the gas phase leaked from the liquid phase and the liquid phase, and are preferably used as an adsorbent and a bad breath removing agent. be able to.

  Table 2 shows the actual measurement data of FIG. Carbonated Fe hydrotalcite and chlorine hydrotalcite showed similar behavior. However, when viewed closely, chlorine-type Fe hydrotalcite tended to adsorb more hydrogen sulfide than carbonate-type Fe hydrotalcite. In the structure of the layered double hydroxide, carbon dioxide is more stable than chlorine as an element of the guest layer, so it is considered that the sulfide was more easily ion-exchanged with chlorine.

  FIG. 9 shows the results of X-ray diffraction of carbonate-type Fe hydrotalcite and chlorine-type Fe hydrotalcite immediately after being produced and dried. The horizontal axis is 2θ (°), and the vertical axis is intensity (arbitrary unit). Co Kα radiation was used as the radiation source. (A) is carbonate type Fe hydrotalcite (denoted as “carbonate type FeHDT” in the figure), and (b) is chlorine type Fe hydrotalcite (denoted as “chlorine type FeHDT” in the figure). is there.

  Also shown in the figure is a diffraction diagram of (c) JCPDS Mg—Fe hydrotalcite (Pyroaurite # 70-2150) (denoted as “Pyroaurite” in the figure). Each sample had a peak at almost the same position as the peak of the diffraction diagram. An unknown peak is not found, and it is judged to have a crystal structure similar to Pyroaurite.

  FIG. 10 shows an enlarged view of 2θ in FIG. 9 of 10 to 40 °. The horizontal axis is 2θ (°), and the vertical axis is intensity (cps). It can be seen that the diffraction peak of the chlorine-type Fe hydrotalcite (b) is on the lower angle side compared to the carbonate-type Fe hydrotalcite (a). Therefore, the C-plane spacing (interlayer distance) is considered to be greater for chlorine-type Fe hydrotalcite than for carbonate-type Fe hydrotalcite.

  In FIG. 11, the result of the X-ray diffraction of the carbonate type Fe hydrotalcite and the chlorine type Fe hydrotalcite after being immersed in the hydrogen sulfide aqueous solution by the inspection apparatus 1 is shown. The horizontal axis is 2θ (°), and the vertical axis is intensity (arbitrary unit). In the figure, a diffraction diagram of JCPDS Mg-Fe hydrotalcite (Pyroaurite # 70-2150) is also shown, and a Miller index (hkl) is also shown.

  Both samples almost coincide with the diffraction diagram of Mg-Fe hydrotalcite. When the peak position was compared with the X-ray diffraction pattern before the adsorption test in FIG. 9, there was not much change in the carbonate type Fe hydrotalcite (a). However, in the chlorine type Fe hydrotalcite (b), the peak position was shifted to the high angle side.

  FIG. 12 shows X-ray diffraction patterns before and after immersion of chlorine-type Fe hydrotalcite. The horizontal axis is 2θ (°), and the vertical axis is intensity (arbitrary unit). (A) is before immersion, and (b) is after immersion. The direction after immersion of (b) is shifted to the high angle side. This indicates that the C-plane spacing has become narrower. Since chlorine ions are 6.7 angstroms and hydrogen sulfide ions are 4.2 angstroms, it is considered that the chlorine ions in the guest layer were replaced with smaller hydrogen sulfide ions.

FIG. 13A shows an infrared absorption spectrum of carbonate-type Fe hydrotalcite, and FIG. 13B shows an infrared absorption spectrum of chlorine-type Fe hydrotalcite. In either case, the horizontal axis represents the wave number (cm ⁻¹ ), and the vertical axis represents the transmittance (arbitrary unit).

In FIG. 13 (a), the broad peak near 3440 cm ⁻¹ is the hydroxyl absorption of the brucite sheet structure of the layered double hydroxide, and the peaks from 2850 cm ⁻¹ to 2950 cm ⁻¹ are the hydrogen of the interlayer water and anions. Absorption of bonds, the peak near 1650 cm ⁻¹ is due to absorption of hydroxyl groups in interlayer water.

The ^{1380 cm} -1, 1050 cm ^{-1 vicinity, 860cm -1, 770cm -1,} the peak of 700 cm ^-1 is due to carbonate ions. Peaks seen from 400 cm ^-1 to 580 cm ^-1 is believed to absorption by binding Fe-O.

FIG. 13B also has a spectrum that is almost the same as that in FIG. However, the absorption peak per 700 cm ⁻¹ corresponding to carbonate ions is not clear in chlorine-based Fe hydrotalcite. Absorption peaks that can be attributed to other carbonate ions are observed, so they are not completely free of carbonate ions. Chlorine ions are considered not to be confirmed by IR because of their strong ion binding properties, and no peak of chlorine ions was observed in FIG. 13 (b).

  FIGS. 14A and 14B show EDS (Energy Dispersive X-ray Spectroscopy) profiles of carbonate-type Fe hydrotalcite and chlorine-type Fe hydrotalcite, respectively.

  Referring to FIG. 14, the horizontal axis is energy (keV), and the vertical axis is the count number. In FIG. 14 (b), a peak of chlorine not found in FIG. 14 (a) was confirmed.

  As described above, together with the results of the powder X-ray diffraction patterns of FIGS. 9 and 11 and the result of the infrared absorption spectrum of FIG. 13, both the carbonate-type Fe hydrotalcite and the chlorine-type Fe hydrotalcite are Mg— Although it has an FeLDH structure, carbonate-type Fe hydrotalcite is carbonate-type, and chlorine-type Fe hydrotalcite contains carbonate ions, but is judged to be chlorine-type.

  Tables 3 and 4 show more detailed elemental analysis results of the EDS shown in FIG. There are five measurement points. The Fe / Mg ratio of Mg—FeLDH (“x” in equation (3) and equation (4)) is x = 0.20 to 0.33. From the results shown in Tables 2 and 3, the carbonic acid type Fe hydrotalcite was x = 0.25, and the chlorine type Fe hydrotalcite was x = 0.25.

  The adsorbent according to the present invention contains Zn hydrotalcite, carbonate-type Fe hydrotalcite, or chlorine-type Fe hydrotalcite, so that it does not select liquid phase or gas phase, and particularly hydrogen sulfide which is a source of bad odor is very good. Adsorb. Therefore, it can be used not only as an adsorbent and a bad breath remover but also as a deodorant.

DESCRIPTION OF SYMBOLS 1 Inspection apparatus 2 Glass flask 3 Funnel 4 Cock 5 Syringe 6 Screw port 10 Hydrogen sulfide aqueous solution 11 Head space

Claims (5)

(2) An adsorbent comprising hydrotalcite having a structure of the formula and adsorbing a volatile sulfur compound in a liquid phase.
[Zn ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] [CO ₃ ²⁻ _{X / 2} · mH ₂ O] (2)
Where 0 <x <1 and m is an integer greater than zero (3) An adsorbent comprising hydrotalcite having a structure of formula (4) or formula (4) and adsorbing a volatile sulfur compound in a liquid phase.
[Mg ²⁺ _1-x + Fe ³⁺ _x (OH) ₂ ] [CO ₃ ²⁻ _{X / 2} · mH ₂ O] (3)
_{^{[Mg 2+ 1-x + Fe}} 3+ x (OH) 2] [Cl - X · mH 2 O] (4)
Where 0 <x <1 and m is an integer greater than zero   The adsorbent according to any one of claims 1 and 2, further comprising water.   The adsorbent according to claim 1, wherein x is 0.33.   A bad breath removing agent comprising the adsorbent according to any one of claims 1 to 4.